Polyphasic sleep involves taking multiple short sleep periods throughout the day instead of getting all your sleep in one long chunk. A popular form of polyphasic sleep, the Uberman sleep schedule, suggests that you sleep 20-30 minutes six times per day, with equally spaced naps every 4 hours around the clock. This means you’re only sleeping 2-3 hours per day. I’d previously heard of polyphasic sleep, but until now I hadn’t come across practical schedules that people seem to be reporting interesting results with.

A normal sleep cycle is 90 minutes, and REM sleep occurs late in this cycle. REM is the most important phase of sleep, the one in which you experience dreams, and when deprived of REM for too long, you suffer serious negative consequences. Polyphasic sleep conditions your body to learn to enter REM sleep immediately when you begin sleeping instead of much later in the sleep cycle. So during the first week you experience sleep deprivation as your body learns to adapt to shorter sleep cycles, but after the adaptation you’ll feel fine, maybe even better than before.